The present invention relates to a lift apparatus and in particular to a dual support post lift apparatus for wheelchairs which is manually movable between a storage position and an operating position and which translationally moves a platform between a raised and lowered operating position.
Various lift apparatus are known and have been made commercially available. Among those are the single support post lift devices in which the support post is fixed to the bed of the vehicle, and the wheelchair or other object being lifted is both translationally moved between a lowered and a raised position and pivotally moved between the raised position and an interior position in the vehicle. Various devices in this general category are illustrated in White, U.S. Pat. No. 2,792,951; Robb, U.S. Pat. No. 3,291,261; Walter, U.S. Pat. No. 3,516,559; Drake, U.S. Pat. No. 4,096,955; Williams, et al., U.S. Pat. No. 3,847,292; and Walter, U.S. Pat. No. 3,516,559.
Other single support post lift devices have also been developed wherein the single support post is not fixed relative to the vehicle but can pivot. Such devices include Landen, U.S. Pat. No. 2,930,499; Southward, et al., U.S. Pat. No. 3,515,294; Adamek, U.S. Pat. No. 3,837,513; and Gates U.S. Pat. No. 4,133,437. However, each of these devices involved sideways platform tilting due to the twisting torque which results as a consequence of lifting a weight such as a wheelchair at a single platform attachment location. Such twisting increases the effective weight which must be lifted and hence increases the required lifting force which must be applied. In addition, each of the above single support post lift apparatus requires separate motions, namely, a vertical motion to lift or lower the wheelchair and a horizontal rotational motion to move the wheelchair and its occupant between the raised position into the interior of the vehicle. By contrast, the present invention includes a dual support post apparatus where the platform is lifted at two front edge locations thereby minimizing the twisting torque and permitting a substantial decrease in the resistance to lifting. Such a decrease in resistance is desirable to enable a lift device to be manually operated in instances where the motive means is inoperable or otherwise when a manual lift apparatus is desired.
Various devices have been developed incorporating dual support structures mounted to the vehicle. For example, in Brown, U.S. Pat. No. 3,305,122, and in Himes, U.S. Pat. No. 3,371,805, dual support posts are interconnected to the vehicle. However, in each of these patents, the support posts are fixed to the vehicle and hence immovable. The raised position of the platform is the storage position and no further movement structure is therefore required.
Other patents incorporating dual support posts attached at two locations along one edge of a platform include Simonelli, et al., U.S. Pat. No. 3,651,965; Fowler, Jr., U.S. Pat. No. 3,710,962; Horowitz, U.S. Pat. No. 3,637,097; and Deacon, U.S. Pat. No. 3,913,759. In each of these patents, however, the support posts are stationary, and movement of the platform between an operating position and a storage position is effected by other means such as pivotal movement about the stationary supporting posts as in the Horowitz patent and the Deacon patent or translational movement relative to the stationary support posts as in the Fowler patent.
Finally, in the Simonelli, et al. patent, the support posts are movable into a storage position, but such movement is by pivotal motion about an axis in the plane of the bed of the vehicle and involves pivotal lifting of the entire lift device.
Although all of the above devices provide certain features and advantages for certain applications, there is still a need for an inexpensive, simple lift device which is suitable for raising and lowering a wheelchair from a vehicle in a safe and secure manner. In the least expensive form of the invention it is therefore desirable to eliminate the motors and provide for manual operation. It will be appreciated that in order to provide a lift apparatus capable of lifting a wheelchair and its occupant through manual cranking of the lift, it is necessary to provide mechanical features which decrease resistance to lifting. In accordance with this objective, the present invention comprises a unique apparatus wherein the platform is movably attached at each corner to a different vertically stationary support post to thereby eliminate the twisting torque and associated increased binding forces.
The present invention also preferably incorporates ball-type lead screws which provide a long gently sloping circular ramp to enable the platform and wheelchair to be more easily lifted (although, of course, more rotations of a crank member are required).
The present invention is further provided with a translational or pivotal means of moving the entire support assembly between the raised outwardly extended operating position and a storage position inside the vehicle without the necessity of supporting and moving the wheelchair during such movement. Hence, the additional weight of the wheelchair and occupant is not carried by the lift apparatus between the storage or interior position and the raised operating position as in other prior art patents.
The present invention also provides a novel interior safety flap mechanism; a novel apparatus for folding the platform into the storage position which allows the lift apparatus to be stored more compactly and also allows a smaller access opening to be used in the pivotal support assembly embodiment of the invention; a novel inboard safety flap apparatus on the platform itself; and a novel switch apparatus which will disable the motor (if one is used) when the platform is in the fully raised position, or is in a nonextended position.
Finally, the present invention incorporates, in one embodiment, a novel translational track mechanism for moving the entire support assembly, including the two vertically stationary posts and associated apparatus, between the operating position and the storage position.
It will, of course, be appreciated that while the present lift apparatus is particularly useful when it is mounted to a vehicle adjacent an access opening, the lift apparatus may also be utilized across any access opening such as the access opening between any two locations where there is a need to go from one vertical level to another. However, for simplicity of explanation reference hereafter is with respect to an access opening of a vehicle.